Abstract: Disclosed herein is a portable ventilator and a method for providing an oscillatory flow to a subject in need thereof. The method comprises: (a) forming a gas mixture comprising pure oxygen and air; (b) converting the gas mixture into the oscillatory flow by applying thereto a predetermined oscillatory frequency and a predetermined ventilatory duration; (c) outputting the oscillatory flow of the step (b) at a first jet pressure, in which the outputted oscillatory flow has a first flow rate; and (d) modulating the outputted oscillatory flow of the step (c) by, (i) varying the respective amounts of the pure oxygen and the air in the gas mixture; or (ii) varying the predetermined ventilatory duration of the step (b), in which if the fist jet pressure is smaller than the predetermined jet pressure, then decreases the predetermined ventilatory duration; or if the first jet pressure is greater than the predetermined jet pressure, then increases the predetermined ventilatory duration.